Method of manufacturing a piezoelectric/electrostrictive device

ABSTRACT

There is disclosed a piezoelectric/electrostrictive porcelain composition capable of manufacturing, at a comparatively low sintering temperature, a piezoelectric/electrostrictive body which is dense and superior in crystallinity and which has satisfactory piezoelectric/electrostrictive characteristics so that deviation of the composition is not easily generated. The piezoelectric/electrostrictive porcelain composition contains as a major component a piezoelectric/electrostrictive porcelain composition component including a PbMg 1/3 Nb 2/3 O 3 —PbZrO 3 —PbTiO 3  ternary solid solution system composition and NiO or including a Pb(Mg, Ni) 1/3 Nb 2/3 O 3 —PbZrO 3 —PbTiO 3  ternary solid solution system composition, and further contains lead germanate.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 11/321,281filed Dec. 29, 2005, now U.S. Pat. No. 7,425,790, the entirety of whichis incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a piezoelectric/electrostrictiveporcelain composition, a piezoelectric/electrostrictive device, and amethod of manufacturing a piezoelectric/electrostrictive device.

BACKGROUND OF THE INVENTION

Heretofore, piezoelectric/electrostrictive devices have been known to becapable of controlling micro displacement on the order of sub-microns.Piezoelectric/electrostrictive devices are especially suitable for thecontrol of the micro displacement. In the device, apiezoelectric/electrostrictive body (piezoelectric/electrostrictiveportion) formed of a piezoelectric/electrostrictive porcelaincomposition and an electrode portion to which a voltage is applied arelaminated on a substrate made of a ceramic. Additionally, the device hassuperior characteristics such as a high electromechanical conversionefficiency, a high-speed response, a high durability, and a reducedpower consumption. The piezoelectric/electrostrictive device is used invarious applications such as a piezoelectric pressure sensor, a probemoving mechanism of a scanning type tunnel microscope, a rectilinearguide mechanism in an ultra-precise working device, a servo valve forhydraulic control, a head of a VTR device, a pixel constituting a flatpanel type image display device, and a head of an ink jet printer.

Moreover, the piezoelectric/electrostrictive porcelain compositionconstituting the piezoelectric/electrostrictive body is also variouslyinvestigated. For example, there has been disclosed aPb(Mg_(1/3)Nb_(2/3))O₃—PbTiO₃—PbZrO₃ ternary solid solution systemcomposition, or a piezoelectric/electrostrictive porcelain compositionin which a part of Pb in the composition is replaced with Sr, La or thelike (see, e.g., Japanese Patent Publication No. 44-17103 and JapanesePatent Publication No. 45-8145). As to thepiezoelectric/electrostrictive body itself which is the most importantportion that determines a piezoelectric/electrostrictive characteristicof the piezoelectric/electrostrictive device, thepiezoelectric/electrostrictive device is expected to be obtained whichhas a superior piezoelectric/electrostrictive characteristic (e.g.,piezoelectric d constant).

On the other hand, it is disclosed that when thepiezoelectric/electrostrictive body is formed using apiezoelectric/electrostrictive porcelain composition containing as amajor component a predetermined PMN-PZ-PT ternary solid solution systemcomposition containing Ni or oxide thereof, it is possible tomanufacture a piezoelectric/electrostrictive device which has superiorpiezoelectric/electrostrictive characteristics and whose linearity of aflexural displacement with respect to an electric field is high up to ahigh electric field region (see, e.g., Japanese Patent ApplicationLaid-Open No. 2002-217464 and Japanese Patent Application Laid-Open No.2002-217465).

However, a raw piezoelectric/electrostrictive material needs to besintered at a high temperature of 1200° C. or more so that thepiezoelectric/electrostrictive body is denser, superior incrystallinity, and exhibits high piezoelectric/electrostrictivecharacteristics. Therefore, in addition to the problem that energy costsare high, there is a problem in that since it is difficult to use an Agelectrode or an Ag—Pd electrode having a comparatively low meltingpoint, an electrode containing expensive Pt has to be used in manycases, and the article lacks in versatility. An element such as Pb or Nicontained in the piezoelectric/electrostrictive porcelain composition isgradually easily evaporated on high-temperature conditions at 1200° C.or more. Therefore, there are problems in that the finally resultantcomposition of the piezoelectric/electrostrictive body easily deviatesfrom the expected composition, and in that it is difficult to obtain apiezoelectric/electrostrictive body exhibiting the desiredpiezoelectric/electrostrictive characteristics.

SUMMARY OF THE INVENTION

The present invention has been developed in view of such conventionaltechnical problems, and an object thereof is to provide apiezoelectric/electrostrictive porcelain composition capable ofmanufacturing a piezoelectric/electrostrictive body which is dense andsuperior in crystallinity and which has satisfactorypiezoelectric/electrostrictive characteristics at a comparatively lowsintering temperature at which the composition does not easily deviate.An object of the present invention is to provide apiezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body which is dense and superior incrystallinity and which has satisfactory piezoelectric/electrostrictivecharacteristics.

Another object of the present invention is to provide a method ofmanufacturing a piezoelectric/electrostrictive device being dense andsuperior in crystallinity and having satisfactorypiezoelectric/electrostrictive characteristics so that it is possible toeasily manufacture the piezoelectric/electrostrictive device withouteasily causing deviation of a composition in apiezoelectric/electrostrictive body or the like.

As a result of intensive investigation by the present inventors in orderto achieve these objects, it has been found that the above-describedobjects can be achieved when lead germanate is further contained inpiezoelectric/electrostrictive porcelain composition componentscontaining NiO or a predetermined ternary solid solution systemcomposition including a Ni element in a structure thereof, and thepresent invention has been completed.

That is, according to the present invention, the followingpiezoelectric/electrostrictive porcelain composition,piezoelectric/electrostrictive device, and method of manufacturing apiezoelectric/electrostrictive device are provided.

According to a first aspect of a first embodiment of the presentinvention, a piezoelectric/electrostrictive porcelain composition isprovided which contains as a major component, apiezoelectric/electrostrictive porcelain composition component includinga PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition and NiO or including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition. The composition further contains lead germanate.

According to a second aspect of the present invention, thepiezoelectric/electrostrictive porcelain composition according to theabove first aspect is provided, wherein thepiezoelectric/electrostrictive porcelain composition component containsthe PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition as the main component, and 0.05 to 3% by mass of NiO, in acase where the piezoelectric/electrostrictive porcelain compositioncomponent includes the PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition and NiO.

According to a third aspect of the present invention, thepiezoelectric/electrostrictive porcelain composition according to theabove second aspect is provided, wherein thePbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition is represented by the following composition formulaPb_(x){(Mg_(y/3)Nb_(2/3))_(a)Ti_(b)Zr_(c)O₃  (1),

wherein 0.95≦x≦1.05, 0.8≦y≦1.0, and a, b, and c are decimals (with theproviso that a+b+c=1.00) in a range surrounded with (a, b, c)=(0.550,0.425, 0.025), (0.550, 0.325, 0.125), (0.375, 0.325, 0.300), (0.050,0.425, 0.525), (0.050, 0.525, 0.425), and (0.375, 0.425, 0.200) in acoordinate whose coordinate axes are a, b, and c described above.

According to a fourth aspect of the present invention, thepiezoelectric/electrostrictive porcelain composition according to thefirst aspect is provided, wherein the Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition is represented by the following composition formula (2) in acase where the piezoelectric/electrostrictive porcelain compositioncomponent includes the Pb(Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternarysolid solution system composition:Pb_(x){(Mg_(1-y)Ni_(y))_((1/3))×_(a)Nb_(2/3)}_(b)Ti_(c)Zr_(d)O₃  (2),

wherein 0.95≦x≦1.05, 0.05≦y≦0.20, 0.90≦a≦1.10, and b, c, and d aredecimals (with the proviso that (b+c+d)=1.000) in a range surroundedwith (b, c, d)=(0.550, 0.425, 0.025), (0.550, 0.325, 0.125), (0.375,0.325, 0.300), (0.050, 0.425, 0.525), (0.050, 0.525, 0.425), and (0.375,0.425, 0.200) in a coordinate whose coordinate axes are b, c, and ddescribed above.

According to a fifth aspect of the present invention, thepiezoelectric/electrostrictive porcelain composition according to anyone of the above aspects contains 0.3 to 4% by mass of lead germanate.

According to a sixth aspect of the present invention, thepiezoelectric/electrostrictive porcelain composition according to anyone of the above aspects is provided, wherein the lead germanate is atleast one kind of material selected from the group consisting of PbGeO₃,Pb₅Ge₃O₁₁, Pb₃GeO₅, an eutectic of PbGeO₃ and Pb₅Ge₃O₁₁, and an eutecticof Pb₅Ge₃O₁₁ and Pb₃GeO₅.

According to a second embodiment of the present invention, apiezoelectric/electrostrictive device is provided, comprising apiezoelectric/electrostrictive body constituted by sintering thepiezoelectric/electrostrictive porcelain composition according to anyone of the above aspects and an electrode electrically connected to thepiezoelectric/electrostrictive body.

According to a first aspect of the second embodiment of the presentinvention, in the piezoelectric/electrostrictive device, thepiezoelectric/electrostrictive body comprises a large number ofpiezoelectric/electrostrictive porcelain grains formed of thepiezoelectric/electrostrictive porcelain composition component, andwherein a grain boundary phase interposed between at least a part of thepiezoelectric/electrostrictive porcelain grains and containing leadgermanate as a major component.

According to a second aspect of the second embodiment of the presentinvention, in the piezoelectric/electrostrictive, thepiezoelectric/electrostrictive body and the electrode have film-likeshapes, wherein the piezoelectric/electrostrictive device furthercomprises a substrate made of a ceramic, and wherein thepiezoelectric/electrostrictive body is solidly attached onto thesubstrate directly or via the electrode.

According to a third aspect of the second embodiment of the presentinvention, the piezoelectric/electrostrictive device according to anyone of the above aspects of the second embodiment is provided, whichfurther comprises a plurality of piezoelectric/electrostrictive bodies,and a plurality of electrodes, wherein the plurality ofpiezoelectric/electrostrictive bodies are alternately sandwiched andlaminated between the plurality of electrodes.

A third embodiment of the present invention provides a method ofmanufacturing a piezoelectric/electrostrictive device that is providedwith a piezoelectric/electrostrictive body and an electrode electricallyconnected to the piezoelectric/electrostrictive body. A first methodcomprises the steps of mixing and sintering first particles containing,as a major component, a piezoelectric/electrostrictive porcelaincomposition component including a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ternary solid solution system composition and NiO or including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, and containing second particles formed of lead germanate tothereby form a piezoelectric/electrostrictive body (hereinafter referredto as “the first method of manufacturing apiezoelectric/electrostrictive device”).

According to a first aspect of the first method of manufacturing thepiezoelectric/electrostrictive device according to the presentinvention, an average particle diameter of the second particles issmaller than that of the first particles.

According to a second aspect of the first method of manufacturing thepiezoelectric/electrostrictive device according to the presentinvention, the first and second particles are mixed and sintered tothereby form the piezoelectric/electrostrictive body into a film shapeand solidly attach the piezoelectric/electrostrictive body onto thesubstrate made of the ceramic directly or via the film-like electrode.

According to another aspect of the third embodiment of the presentinvention, a second method of manufacturing apiezoelectric/electrostrictive device that is provided with apiezoelectric/electrostrictive body and an electrode electricallyconnected to the piezoelectric/electrostrictive body. The methodcomprises the steps of mixing first particles containing, as a majorcomponent, a piezoelectric/electrostrictive porcelain compositioncomponent including a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition and NiO or including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition with second particles made of lead germanate to obtain amixture, calcining the resultant mixture at a temperature of 550 to 900°C. to obtain a calcined body, grinding the resultant calcined body toobtain ground particles, and sintering the resultant grinded particlesto form the piezoelectric/electrostrictive body (hereinafter referred toas “the second method of manufacturing a piezoelectric/electrostrictivedevice”).

According to a first aspect of the second method of manufacturing thepiezoelectric/electrostrictive device according to the presentinvention, the ground particles are piezoelectric/electrostrictiveporcelain particles containing the piezoelectric/electrostrictiveporcelain composition component as a major component, and 30% by mass ormore of coated particles at least a part of which on an outer peripheralsurface are coated with lead germanate.

According to a second aspect of the second method of manufacturing thepiezoelectric/electrostrictive device according to the presentinvention, the ground particles are sintered to thereby form thepiezoelectric/electrostrictive body into a film shape and solidly attachthe piezoelectric/electrostrictive body onto a substrate made of aceramic directly or via the film-like electrode.

In the first and second methods of manufacturing thepiezoelectric/electrostrictive device according to the above aspects,the lead germanate is at least one kind selected from the groupconsisting of PbGeO₃, Pb₅Ge₃O₁₁, Pb₃GeO₅, an eutectic of PbGeO₃ andPb₅Ge₃O₁₁, and an eutectic of Pb₅Ge₃O₁₁ and Pb₃GeO₅.

In the first and second methods of manufacturing thepiezoelectric/electrostrictive device according to the above aspects,the first and second particles are mixed after thermally treating thefirst particles beforehand at a temperature of 1100 to 1300° C.

The piezoelectric/electrostrictive device described above includes apiezoelectric/electrostrictive device comprising apiezoelectric/electrostrictive body formed ofpiezoelectric/electrostrictive porcelain composition, and electrodesformed on the piezoelectric/electrostrictive body applying voltage onthe piezoelectric/electrostrictive body. In addition, thepiezoelectric/electrostrictive device described above also includes apiezoelectric/electrostrictive device laminating apiezoelectric/electrostrictive body (piezoelectric/electrostrictiveportion) and electrodes on the substrate made of ceramics. Moreover, thepiezoelectric/electrostrictive device described above also includes apiezoelectric/electrostrictive device alternately laminating a pluralityof piezoelectric/electrostrictive bodies (piezoelectric/electrostrictiveportions) formed of piezoelectric/electrostrictive porcelain compositionand a plurality of electrodes.

The composite piezoelectric/electrostrictive porcelain composition ofthe present invention makes it possible to manufacture apiezoelectric/electrostrictive body which is dense and superior incrystallinity and which has satisfactory piezoelectric/electrostrictivecharacteristics at a comparatively low sintering temperature at whichdeviation of the composition or the like is not easily caused.

The piezoelectric/electrostrictive device of the present invention isprovided with a piezoelectric/electrostrictive body which is dense andsuperior in crystallinity and which has satisfactorypiezoelectric/electrostrictive characteristics, and produces an effectthat a large displacement is exhibited.

According to the methods of manufacturing thepiezoelectric/electrostrictive device of the present invention, it ispossible to easily manufacture the piezoelectric/electrostrictive devicewhich is dense and superior in crystallinity and which has satisfactorypiezoelectric/electrostrictive characteristics without easily causingthe deviation of the composition or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically showing one embodiment of apiezoelectric/electrostrictive device according to the presentinvention.

FIG. 2 is a sectional view schematically showing another embodiment ofthe piezoelectric/electrostrictive device according to the presentinvention.

FIG. 3 is a sectional view schematically showing still anotherembodiment of the piezoelectric/electrostrictive device according to thepresent invention.

FIG. 4 is a sectional view schematically showing still anotherembodiment of the piezoelectric/electrostrictive device of the presentinvention.

FIG. 5( a) is a top plan view schematically showing a further embodimentof the piezoelectric/electrostrictive device of the present invention.

FIG. 5( b) is a sectional view schematically showing a still furtherembodiment of the piezoelectric/electrostrictive device of the presentinvention.

FIG. 6 is a sectional view showing one example of the embodiment shownin FIG. 3 in more detail.

FIG. 7 is a sectional view showing another example of the embodimentshown in FIG. 3 in more detail.

FIG. 8 is a sectional view showing still another example of theembodiment shown in FIG. 3 in more detail.

FIG. 9 is a sectional view showing a further example of the embodimentshown in FIG. 3 in more detail.

FIG. 10 is a sectional view showing a further example of the embodimentshown in FIG. 3 in more detail.

FIG. 11 is a sectional view showing a still further example of theembodiment shown in FIG. 3 in more detail.

FIG. 12( a) is a sectional view along X-X′ of the embodiment shown inFIG. 6.

FIG. 12( b) is a top plan view of the embodiment shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

A preferred mode for carrying out the present invention will bedescribed hereinafter, but it should be understood that the presentinvention is not limited to the following embodiments, and the presentinvention includes appropriate alterations, modifications and the likeadded to the following embodiments based on the ordinary knowledge of aperson skilled in the art without departing from the scope of thepresent invention. It is to be noted that when “a method ofmanufacturing a piezoelectric/electrostrictive device of the presentinvention (the present embodiment)” is simply mentioned in the presentspecification, both of first and second methods of manufacturing thepiezoelectric/electrostrictive devices are indicated.

One embodiment of a piezoelectric/electrostrictive porcelain compositionof the present invention relates to a compositepiezoelectric/electrostrictive porcelain composition containing, as amajor component, a piezoelectric/electrostrictive porcelain compositioncomponent comprising a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition and NiO, or a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, and further containing lead germanate. Details will bedescribed hereinafter.

The piezoelectric/electrostrictive porcelain composition component whichis the main component of the composite piezoelectric/electrostrictiveporcelain composition of the present embodiment is (1) the componentcontaining the PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solutionsystem composition and NiO, or (2) the component containing the Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition.

Moreover, the piezoelectric/electrostrictive porcelain composition ofthe present embodiment further contains lead germanate. In general, themelting point of lead germanate is low as compared with the temperature(1200° C. or more) at which a conventional PZT-basedpiezoelectric/electrostrictive porcelain composition is sintered.Therefore, when the piezoelectric/electrostrictive porcelain compositioncontains a predetermined amount of lead germanate, it is possible tomanufacture the piezoelectric/electrostrictive body or portion which isdense and superior in crystallinity and at a sintering temperature lowerthan a conventional temperature. Furthermore, the present embodiment canalso contribute to the reduction of energy costs or the amount ofdischarged carbon dioxide. Moreover, it is possible to use an Ag—Pdelectrode whose melting point is lower than that of a Pt electrode.

Furthermore, since the composition can be sintered at a low sinteringtemperature, it is possible to inhibit elements such as Pb and Ni frombeing evaporated during high temperature sintering. Therefore, it ispossible to obtain a piezoelectric/electrostrictive body or the like inwhich the composition of the resultant piezoelectric/electrostrictivebody or portion does not easily deviate from the expected composition,and which exhibits desired piezoelectric/electrostrictivecharacteristics. For example, the sintering of a ceramic substrate ispossible at a lower sintering temperature. Therefore, it is possible toinhibit reactions between elements constituting thepiezoelectric/electrostrictive porcelain composition and the ceramicsubstrate. Consequently, the composition of the resultantpiezoelectric/electrostrictive portion does not easily deviate from theexpected composition.

When the piezoelectric/electrostrictive porcelain composition componentcontains a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solutionsystem composition and NiO, the piezoelectric/electrostrictive porcelaincomposition component preferably contains thePbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition as a major component, and preferably 0.05 to 3%, morepreferably 0.07 to 2.5, especially preferably 0.10 to 2% by mass of NiO.When a content of NiO is defined in the above-described numerical valuerange, it is possible to inhibit a hetero-phase in the resultantpiezoelectric/electrostrictive body and portion. It is possible to formthe piezoelectric/electrostrictive body or portion in which an occupyingratio of a perovskite phase contributing to an electric field inducedstrain is large and which is dense and superior in crystallinity andwhich has remarkably high piezoelectric/electrostrictivecharacteristics.

It is to be noted that the “main component” in the “thePbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition as the main component” mentioned in the presentspecification indicates that a content ratio of thePbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition is 99.5% or more, preferably 99.8% or more by mass withrespect to all of the piezoelectric/electrostrictive porcelaincomposition components excluding NiO.

In the piezoelectric/electrostrictive porcelain composition of thepresent embodiment, the PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition is preferably represented by the followingcomposition formula (1) because it is possible to form thepiezoelectric/electrostrictive body or portion having higherpiezoelectric/electrostrictive characteristics:Pb_(x){(Mg_(y/3)Nb_(2/3))_(a)Ti_(b)Zr_(c)O₃  (1),

wherein 0.95≦x≦1.05, 0.8≦y≦1.0, and a, b, and c are decimals (with theproviso that a+b+c=1.00) in a range surrounded with (a, b, c)=(0.550,0.425, 0.025), (0.550, 0.325, 0.125), (0.375, 0.325, 0.300), (0.050,0.425, 0.525), (0.050, 0.525, 0.425), and (0.375, 0.425, 0.200) in acoordinate whose coordinate axes are a, b, and c described above.

On the other hand, when the piezoelectric/electrostrictive porcelaincomposition component contains a Pb (Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, the Pb(Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition is preferably represented by the followingcomposition formula (2) because it is possible to form thepiezoelectric/electrostrictive body or portion having higherpiezoelectric/electrostrictive characteristics:Pb_(x){(Mg_(1-y)Ni_(y))_((1/3))×_(a)Nb_(2/3)}_(b)Ti_(c)Zr_(d)O₃  (2),

wherein 0.95≦x≦1.05, 0.05≦y≦0.20, 0.90≦a≦1.10, and b, c, and d aredecimals (with the proviso that (b+c+d)=1.000) in a range surroundedwith (b, c, d)=(0.550, 0.425, 0.025), (0.550, 0.325, 0.125), (0.375,0.325, 0.300), (0.050, 0.425, 0.525), (0.050, 0.525, 0.425), and (0.375,0.425, 0.200) in a coordinate whose coordinate axes are b, c, and ddescribed above.

In the piezoelectric/electrostrictive porcelain composition of thepresent embodiment, it is preferable to replace Pb among thepiezoelectric/electrostrictive porcelain composition components with atleast one kind of element selected from the group consisting of Sr, Ba,La, and Bi because it is possible to further enhance thepiezoelectric/electrostrictive characteristics of the resultantpiezoelectric/electrostrictive article or portion.

When Pb is replaced with at least one kind of element selected from thegroup consisting of Sr, Ba, La, and Bi at a high replacement ratio, thepiezoelectric/electrostrictive characteristics of the resultantpiezoelectric/electrostrictive body or portion are deteriorated, andfluctuations of the piezoelectric/electrostrictive characteristics dueto a temperature change increase in some case. Therefore, when a part ofPb is replaced with Sr and/or Ba, preferably 3 to 10 mol %, morepreferably 5 to 8 mol % of Pb is replaced with Sr and/or Ba. When a partof Pb is replaced with La and/or Bi, preferably 0.2 to 1.0 mol %, morepreferably 0.4 to 0.9 mol % of Pb is replaced with La and/or Bi.

In the piezoelectric/electrostrictive porcelain composition of thepresent embodiment, it is preferable to replace Ti among thepiezoelectric/electrostrictive porcelain composition components with atleast one kind of element selected from the group consisting of Nb, Ta,W, and Mo because the piezoelectric/electrostrictive characteristics ofthe resultant piezoelectric/electrostrictive body or portion can befurther enhanced. It is to be noted that preferably 3 to 10 mol %, morepreferably 5 to 8 mol % of Ti is replaced with at least one kind ofelement selected from the group consisting of Nb, Ta, W, and Mo.

In the piezoelectric/electrostrictive porcelain composition of thepresent embodiment, it is preferable to contain at least one kind ofcompound selected from the group consisting of MnO₂, CeO₂, and SiO₂,because it is possible to further enhance thepiezoelectric/electrostrictive characteristics of the resultantpiezoelectric/electrostrictive body or portion. It is to be noted thatthe content ratio of at least one kind of compound selected from thegroup consisting of MnO₂, CeO₂, and SiO₂ is preferably 0.05 to 5% bymass, more preferably 0.1 to 2% by mass.

The piezoelectric/electrostrictive porcelain composition of the presentembodiment is essentially preferably formed ofpiezoelectric/electrostrictive porcelain composition componentsincluding a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solutionsystem composition and NiO, or a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, and lead germanate. It is to be noted that in thepiezoelectric/electrostrictive porcelain composition of the presentembodiment, the content of lead germanate is preferably 0.3 to 4% bymass, more preferably 0.3 to 3% by mass, especially preferably 0.3 to1.8% by mass. When the content of lead germanate is less than 0.3% bymass, the composition is not densified at a low sintering temperature insome case. On the other hand, when the content of lead germanate exceeds4% by mass, a portion occupied by lead germanate having whosepiezoelectric/electrostrictive characteristics are low or absentincreases, and therefore the piezoelectric/electrostrictivecharacteristics are sometimes deteriorated.

In the piezoelectric/electrostrictive porcelain composition of thepresent embodiment, lead germanate is preferably at least one of PbGeO₃,Pb₅Ge₃O₁₁, Pb₃GeO₅, an eutectic of PbGeO₃ and Pb₅Ge₃O₁₁, and an eutecticof Pb₅Ge₃O₁₁ and Pb₃GeO₅. In the case where the lead germanate isPbGeO₃, even when the lead germanate reacts with the perovskite and isdissolved, PbO rarely becomes hetero-phase, and the characteristics arepreferably inhibited from being deteriorated. In the case where the leadgermanate is Pb₅Ge₃O₁₁, since Pb₅Ge₃O₁₁ itself is ferroelectric, thepiezoelectric/electrostrictive characteristics of the resultantpiezoelectric/electrostrictive body or portion can be preferablyinhibited from being deteriorated. Furthermore, in a case where leadgermanate is Pb₃GeO₅, since Pb in Pb₃GeO₅ is evaporated, Pb can beinhibited from being evaporated from the piezoelectric/electrostrictiveporcelain composition components, and the characteristics of thepiezoelectric/electrostrictive porcelain composition can be preferablyinhibited from being deteriorated.

On the other hand, the eutectic of PbGeO₃ and Pb₅Ge₃O₁₁ or that ofPb₅Ge₃O₁₁ and Pb₃GeO₅ has a melting point (melting point of the eutecticof PbGeO₃ and Pb₅Ge₃O₁₁=710° C., melting point of eutectic of Pb₅Ge₃O₁₁and Pb₃GeO₅) that is lower than that of each single compound (meltingpoint of PbGeO₃=810° C., melting point of Pb₅Ge₃O₁₁=743° C., meltingpoint of Pb₃GeO₅=745° C.). Therefore, it is preferably possible tomanufacture the piezoelectric/electrostrictive body or portion which isdense and superior in crystallinity while exhibiting superiority in acase where each single compound is used at a lower sinteringtemperature.

Additionally, in Japanese Patent No. 2643154, there is disclosed apyroelectric porcelain composition capable of obtaining a pyroelectricporcelain which contains a Pb[(Mg_(1/3)Nb_(2/3)), Ti, Zr]O₃-basedporcelain composition as a major component, and Pb₅Ge₃O₁₁ as asub-component and which is dense and which has a large mechanicalstrength. However, this publication does not disclose or suggest thatNiO is contained in the porcelain composition, the publication does notdisclose or suggest effects, such as inhibition of hetero-phaseformation or increase of the ratio occupied by the perovskite phase,produced in a case where NiO is contained in the porcelain composition.As to lead germanate, Pb₅Ge₃O₁₁ is only disclosed. There is nodisclosure or suggestion of superiority in a case where another compoundor eutectic is contained, and the constitution is apparently differentfrom that of the piezoelectric/electrostrictive porcelain composition ofthe present invention.

To obtain a Pb-based piezoelectric/electrostrictive porcelaincomposition, it is usually necessary to sinter the composition at a hightemperature of about 1200° C. Therefore, it is necessary to add alow-melting-point material such as a glass in order to sinter thecomposition at a low temperature of about 1000° C. and obtain thepiezoelectric/electrostrictive porcelain composition. However, thepiezoelectric/electrostrictive porcelain composition sometimes reactswith the additive depending on a combination of thepiezoelectric/electrostrictive porcelain composition with the additive.Even if the composition is sintered at a low temperature, thecharacteristics are remarkably deteriorated in some case. In the presentembodiment, since the piezoelectric/electrostrictive porcelaincomposition contains NiO, there are advantages in that the reactivitywith the lead germanate is low, and the characteristics are onlyslightly deteriorated.

Next, an embodiment of the piezoelectric/electrostrictive device of thepresent invention will be described. In the present embodiment, thepiezoelectric/electrostrictive device is provided with apiezoelectric/electrostrictive body constituted by sintering any of thepiezoelectric/electrostrictive porcelain compositions according to theembodiment of the present invention described above, and an electrodeelectrically connected to this piezoelectric/electrostrictive body. Thatis, in the present embodiment, the piezoelectric/electrostrictive deviceis provided with a piezoelectric/electrostrictive body constituted bysintering a piezoelectric/electrostrictive porcelain compositioncontaining, as a major component, a piezoelectric/electrostrictiveporcelain composition components including aPbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition and NiO, or a Pb(Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ternary solid solution system composition, and further containing leadgermanate. An electrode is electrically connected to thispiezoelectric/electrostrictive body.

As described above, in the embodiment of the present invention, thepiezoelectric/electrostrictive porcelain composition contains, as amajor component, the piezoelectric/electrostrictive porcelaincomposition component including NiO or a predetermined ternary solidsolution system composition containing an Ni element in a structurethereof, and further contains lead germanate. Therefore, in thepiezoelectric/electrostrictive body constituted by sintering thispiezoelectric/electrostrictive porcelain composition, the hetero-phaseis inhibited from being formed, and the ratio occupied by the perovskitephase constituting an electric field induced strain is large. Moreover,the body is dense and superior in crystallinity, and has satisfactorypiezoelectric/electrostrictive characteristics. Furthermore, since leadgermanate is included, the body is obtained at a comparatively lowsintering temperature. Therefore, in the piezoelectric/electrostrictivedevice of the present embodiment, it is possible to positively use anAg—Pd electrode whose melting point is lower than that of a Ptelectrode, and the device is also superior in energy cost orversatility.

In the piezoelectric/electrostrictive device of the present embodiment,the piezoelectric/electrostrictive body constituting the device ispreferably formed of a large number of piezoelectric/electrostrictiveporcelain grains containing the piezoelectric/electrostrictive porcelaincomposition components, and a grain boundary phase interposed between atleast a part of the piezoelectric/electrostrictive porcelain grains andcontaining lead germanate as the main component. That is, the grainboundary phase containing, as the main component, lead germanate havinga specific permittivity larger than that of pores exists so as to fillin gaps among the large number of piezoelectric/electrostrictiveporcelain grains formed of the piezoelectric/electrostrictive porcelaincomposition components. Therefore, the piezoelectric/electrostrictivedevice of the present embodiment has more satisfactorypiezoelectric/electrostrictive characteristics.

Moreover, in the piezoelectric/electrostrictive device of the presentembodiment, a germanium (Ge) element constituting the lead germanate isdiffused in the piezoelectric/electrostrictive porcelain grainsconstituting the piezoelectric/electrostrictive body. This is preferableto enhance the strength of the piezoelectric/electrostrictive body. Itis to be noted that EPMA analysis can be used to determine whether ornot the Ge element is diffused in the piezoelectric/electrostrictiveporcelain grains or to which extent the element is diffused (diffusiondepth).

In the piezoelectric/electrostrictive device of the present embodiment,an average grain diameter of crystal grains constituting thepiezoelectric/electrostrictive body is preferably 0.1 to 10 μm, morepreferably 0.2 to 8.5 μm, especially preferably 0.3 to 7 μm. When theaverage grain diameter is less than 1 μm, a domain does not sufficientlydevelop in the piezoelectric/electrostrictive body, and deteriorationsof the piezoelectric/electrostrictive characteristics are caused easilyin some cases. On the other hand, when the average grain diameterexceeds 10 μm, the domain in the piezoelectric/electrostrictive bodysufficiently develops, but the domain does not move easily, and thepiezoelectric/electrostrictive characteristics are reduced in somecases. It is to be noted that the piezoelectric/electrostrictive bodyand the electrode constituting the piezoelectric/electrostrictive deviceof the present embodiment can be formed into various shapes. Typicallypreferable examples of the shape include a block shape (so-called bulkbody), a sheet shape (film shape) and a multilayered constitution.

Next, the embodiment of the piezoelectric/electrostrictive device of thepresent invention will be described specifically with reference to thedrawings. FIG. 1 is a sectional view schematically showing oneembodiment of the piezoelectric/electrostrictive device of the presentinvention. As shown in FIG. 1, a piezoelectric/electrostrictive device51 of the present embodiment is provided with: a substrate 1 made of aceramic; a film-like piezoelectric/electrostrictive body 2; andfilm-like electrodes 4, 5 electrically connected to thispiezoelectric/electrostrictive body 2, and thepiezoelectric/electrostrictive body 2 is solidly attached onto thesubstrate 1 via the electrode 4. It is to be noted that thepiezoelectric/electrostrictive body may be solidly attached directlyonto the substrate without interposing any electrode. It is to be notedthat “solidly attached” mentioned in the present specification indicatesthat the piezoelectric/electrostrictive body 2 is formed closelyintegrally with the substrate 1 or the electrode 4 by a solid-phasereaction therebetween without using any organic or inorganic adhesive.

The piezoelectric/electrostrictive body 2 of thepiezoelectric/electrostrictive device 51 of the present embodiment isconstituted by sintering any of the piezoelectric/electrostrictiveporcelain compositions according to the above-described embodiment ofthe present invention. That is, in the piezoelectric/electrostrictivedevice 51 of the present embodiment, the piezoelectric/electrostrictivebody 2 is constituted by sintering the piezoelectric/electrostrictiveporcelain composition which contains, as a major component, thepiezoelectric/electrostrictive porcelain composition component includingthe PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition and NiO, or the Pb(Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ternary solid solution system composition, and further contains leadgermanate.

As described above, the piezoelectric/electrostrictive porcelaincomposition contains, as the main component, thepiezoelectric/electrostrictive porcelain composition component includingNiO or the predetermined ternary solid solution system compositioncontaining the Ni element in the structure thereof, and further containslead germanate. Therefore, in the piezoelectric/electrostrictive body 2formed by sintering this piezoelectric/electrostrictive porcelaincomposition, a hetero-phase is inhibited from being formed, and theratio occupied by the perovskite phase contributing to the electricfield induced strain is large. Moreover, the body is dense and superiorin crystallinity. Therefore, in the present embodiment, thepiezoelectric/electrostrictive device 51 provided with thepiezoelectric/electrostrictive body 2 has satisfactorypiezoelectric/electrostrictive characteristics and can obtain a largedisplacement. Furthermore, since the piezoelectric/electrostrictiveporcelain composition contains lead germanate, thepiezoelectric/electrostrictive body 2 can be formed at a comparativelylow sintering temperature. Therefore, it is possible to use an Ag—Pdelectrode whose melting point is lower than that of a Pt electrode. Thedevice is also superior in energy cost or versatility.

In the piezoelectric/electrostrictive device 51 of the presentembodiment, the piezoelectric/electrostrictive body 2 is preferablyformed of a large number of piezoelectric/electrostrictive porcelaingrains containing the piezoelectric/electrostrictive porcelaincomposition components, and a grain boundary phase interposed between atleast a part of the piezoelectric/electrostrictive porcelain grains andcontaining lead germanate as the main component. That is, the grainboundary phase containing lead germanate as the main component exists soas to fill in gaps among the large number ofpiezoelectric/electrostrictive porcelain grains formed of thepiezoelectric/electrostrictive porcelain composition components.Therefore, in the piezoelectric/electrostrictive device 51 of thepresent embodiment, the piezoelectric/electrostrictive body 2 isconstituted to be denser. Therefore, the piezoelectric/electrostrictivedevice 51 can exhibit more satisfactory piezoelectric/electrostrictivecharacteristics and obtain a larger displacement.

Moreover, in the piezoelectric/electrostrictive device 51 of the presentembodiment, a germanium (Ge) element constituting lead germanate isdiffused in the piezoelectric/electrostrictive porcelain grainsconstituting the piezoelectric/electrostrictive body 2. This ispreferable with respect to enhancing the strength of thepiezoelectric/electrostrictive body. It is to be noted that EPMAanalysis can be used to determine whether or not the Ge element isdiffused in the piezoelectric/electrostrictive porcelain grains or todetermine the extent to which the element is diffused (diffusion depth).

In the piezoelectric/electrostrictive device 51 of the presentembodiment, an average grain diameter of crystal grains constituting thepiezoelectric/electrostrictive body 2 is preferably 0.1 to 10 μm, morepreferably 0.2 to 8.5 μm, especially preferably 0.3 to 7 μm. When theaverage grain diameter is less than 1 μm, a domain does not sufficientlydevelop in the piezoelectric/electrostrictive body 2, and deteriorationsof flexural displacement and linearity of the flexural displacement withrespect to an electric field in a high electric field region aredeteriorated in some cases. On the other hand, when the average graindiameter exceeds 10 μm, the domain in the piezoelectric/electrostrictivebody 2 sufficiently develops, but the domain does not move easily, andthe flexural displacement is reduced in some cases.

Moreover, as shown in FIG. 3, in the present embodiment, thepiezoelectric device 51 may have a constitution which is provided with aplurality of piezoelectric/electrostrictive bodies 2, 3, and a pluralityof electrodes 4, 5, and 6 and in which the plurality ofpiezoelectric/electrostrictive bodies 2, 3 are alternately sandwichedand laminated between the plurality of electrodes 4, 5, and 6. Thisconstitution is a so-called multilayered constitution, and a largeflexural displacement can be preferably obtained at a low voltage.

In the piezoelectric/electrostrictive device 51 (see FIG. 1) of thepresent embodiment, the thickness of the piezoelectric/electrostrictivebody 2 is preferably 0.5 to 50 μm, more preferably 0.8 to 40 μm,especially preferably 1.0 to 30 μm. When the thickness of thepiezoelectric/electrostrictive body 2 is less than 0.5 μm, even apiezoelectric/electrostrictive body formed of apiezoelectric/electrostrictive porcelain composition according to thepresent invention is insufficiently densified in some cases. On theother hand, when the thickness of the piezoelectric/electrostrictivebody 2 exceeds 50 μm, contraction stresses of thepiezoelectric/electrostrictive porcelain composition increase at duringsintering, and the substrate 1 needs to be thicker in order to preventfrom the substrate 1 from being broken. Therefore, it is sometimesdifficult to cope with miniaturization of the device. It is to be notedthat as shown in FIG. 3, the thicknesses of thepiezoelectric/electrostrictive bodies 2, 3 in a case where thepiezoelectric/electrostrictive device 51 has a so-called multilayeredconstitution refer to the respective thicknesses of thepiezoelectric/electrostrictive bodies 2, 3.

The substrate constituting the piezoelectric/electrostrictive deviceaccording to the present invention is made of a ceramic, and the kind ofceramic is not restricted. This ceramic preferably contains at least onematerial selected from the group consisting of stabilized zirconiumoxide, aluminum oxide, magnesium oxide, mullite, aluminum nitride,silicon nitride, and glass with respect to providing heat resistance,chemical stability, and insulating properties. Above all, stabilizedzirconium oxide is more preferable because its mechanical strength islarge and its tenacity is superior. It is to be noted that “stabilizedzirconium oxide” refers to zirconium oxide in which phase transition ofcrystals is inhibited by addition of a stabilizer, and partiallystabilized zirconium oxide is included in addition to stabilizedzirconium oxide.

Examples of stabilized zirconium oxide include zirconium oxidecontaining as the stabilizer 1 to 30 mol % of calcium oxide, magnesiumoxide, yttrium oxide, scandium oxide, ytterbium oxide, cerium oxide, oroxide of a rare earth metal. Above all, zirconium oxide containingyttrium oxide as the stabilizer is preferable because the mechanicalstrength of a vibrating portion is especially high. In this case,zirconium oxide preferably contains 1.5 to 6 mol % yttrium oxide, andmore preferably 2 to 4 mol % yttrium oxide. Zirconium oxide morepreferably contains 0.1 to 5 mol % of aluminum oxide. A crystal phase ofstabilized zirconium oxide may be a mixed phase of a cubic system+amonoclinic system, a mixed phase of a tetragonal system+the monoclinicsystem, a mixed phase of the cubic system+the tetragonal system+themonoclinic system or the like. However, a main crystal phase of thetetragonal system, or the mixed phase of the tetragonal system+the cubicsystem, is preferable from viewpoints of strength, tenacity, anddurability.

It is to be noted that the thickness of the substrate is preferably 1 μmto 1 mm, more preferably 1.5 to 500 μm, and especially preferably 2 to200 μm. When the thickness of the substrate is less than 1 μm, themechanical strength of the piezoelectric/electrostrictive device issometimes deteriorated. On the other hand, in the case where thethickness exceeds 1 mm, when voltage is applied to thepiezoelectric/electrostrictive body, the rigidity of the substrateincreases with respect to the generated contraction stress, and theflexural displacement of the piezoelectric/electrostrictive body isreduced in some cases.

However, as shown in FIG. 2, the substrate 1 may be formed into a shapeprovided with a thin portion 1 c whose one surface is provided with asolidly attached surface 1 a and which has the above-describedthickness, and a thick portion 1 b which is thicker than the thinportion 1 c disposed in a portion other than a portion corresponding tothe solidly attached surface 1 a. It is to be noted that the electrode 4(or the piezoelectric/electrostrictive body) is disposed in a regionsubstantially corresponding to the solidly attached surface 1 a. Sincethe substrate 1 is formed into such a shape, it is possible toconstitute a piezoelectric/electrostrictive device whose flexuraldisplacement is sufficient large and whose mechanical strength is large.A common substrate 20 is used in which the shape of the substrate 1shown in FIG. 2 is continuously formed as shown in FIG. 4. On thiscommon substrate 20, there can be disposed a plurality ofpiezoelectric/electrostrictive device units 10 each including a firstpiezoelectric/electrostrictive body 12, a secondpiezoelectric/electrostrictive body 13, and electrodes 4, 5, and 6.

There is not any special restriction on shape of the surface of thesubstrate to which the electrode 4 is solidly attached in FIG. 1 in thepiezoelectric/electrostrictive device of the present invention. Examplesof a suitable surface shape include a rectangular shape, a square shape,a triangular shape, an elliptical shape, a circular shape, a curvedsquare shape, a curved rectangular shape, and a composite shape of acombination of these shapes. There is not any special restriction on theoverall shape of the substrate, and the substrate may have a capsuleshape having an appropriate internal space.

Moreover, as to the shape of the thin portion of the substrate, from theview that the linearity of the flexural displacement with respect to theelectric field is high, the center of the thin portion preferably has ashape that is bent on a side opposite to a side on which thepiezoelectric bodies 2, 3 are disposed as shown in FIG. 7, or asectional shape in a thickness direction that has a so-called W-shape asshown in FIG. 8. In this shape, opposite end portions of the substrateprotrude in a perpendicular direction from a bottom-portion side as seenfrom a center line in a longitudinal direction of the substrate, and thecenter of the shape protrudes upward. It is to be noted that the bentshape shown in FIG. 7 can be formed utilizing contraction in a step ofsintering the respective piezoelectric/electrostrictive bodies 2, 3, andthe W-shape shown in FIG. 8 can be formed by adjusting sinteringcontraction starting timings or sintering contraction amounts of thepiezoelectric/electrostrictive bodies 2, 3 and the shape of the thinportion 1 c.

In the piezoelectric/electrostrictive device of the present invention,the electrode is preferably electrically connected to thepiezoelectric/electrostrictive body, and disposed between the respectivepiezoelectric/electrostrictive bodies. The electrode is preferablydisposed over a region of the piezoelectric/electrostrictive body whichsubstantially contributes to the flexural displacement or the like. Forexample, as shown in FIG. 3, the electrodes 4, 5, and 6 are preferablydisposed in a region having 80% by area including the vicinity of thecentral portion of the surface on which the first and secondpiezoelectric/electrostrictive bodies 12 and 13 are formed.

Moreover, when the common substrate 20 is shared by a plurality ofpiezoelectric/electrostrictive device units 10 a to 10 c as shown inFIGS. 5( a) and 5(b), a lowermost-layer electrode 14 and anuppermost-layer electrode 16 in the respectivepiezoelectric/electrostrictive device units 10 a to 10 c are sharedamong the respective piezoelectric/electrostrictive device units 10 a to10 c. The integral electrode 14 may be disposed in a regioncorresponding to piezoelectric/electrostrictive portions 2 a to 2 c, 3 ato 3 c. Such an integral electrode does not have to be formed into ashape corresponding to each of the individualpiezoelectric/electrostrictive bodies 2 a to 2 c, 3 a to 3 c, andpositioning is facilitated in forming the electrode 14.

In the piezoelectric/electrostrictive device of the present invention,examples of suitable electrode materials include at least one kind ofmetal selected from the group consisting of Pt, Pd, Rh, Au, Ag, and analloy of those metals. Above all, platinum or an alloy containingplatinum as a major component is preferable because it has a high heatresistance during the sintering of the piezoelectric/electrostrictivebody. An alloy such as Ag—Pd is preferably usable because thepiezoelectric/electrostrictive body can be formed at a lower sinteringtemperature. There is not any special restriction on the dimension ofthe electrode. For example, as shown in FIGS. 6, 12(a), and 12(b), therespective electrodes 4, 5, and 6 may be set to an equal width, and therespective electrodes 4, 5, and 6 may be disposed in positions incorresponding to one another in width directions. As shown in FIG. 9,the respective electrodes 4, 5, and 6 are preferably successivelyarranged from the electrode 4 positioned in a lowermost-layer in abroader region including a region corresponding to the electrodepositioned in a lower layer. According to such a constitution, since thepiezoelectric/electrostrictive body positioned in an upper layer can bedistorted to a greater degree than the piezoelectric/electrostrictivebody positioned in the lower layer, a bending efficiency is enhanced,and the flexural displacement can be more effectively developed.

However, in the case where the driving voltage of thepiezoelectric/electrostrictive device is enhanced to obtain a largerflexural displacement, the intermediately positioned electrode 5 ispreferably disposed in a region that is broader than that of each of theelectrodes 4 and 6 positioned in the lower and upper layers,respectively, as shown in FIG. 10. Alternatively, as shown in FIG. 11,the intermediately positioned electrode 5 is preferably disposed in aregion that is smaller than that of each of the electrodes 4 and 6.According to such a constitution, an electric field is hardly applied tothe vicinity of each end portion (in a short direction) in which thethicknesses of the piezoelectric/electrostrictive bodies 2, 3 are easilyreduced, and dielectric breakdown of the piezoelectric/electrostrictivebodies 2, 3 can be avoided.

In the case where a breadth difference is made in the region in whichthe electrode is disposed, the breadth difference is preferablyoptimized in consideration of the electric field distribution. Forexample, the electrodes 4 and 5 (or 5 and 6) are disposed adjacent toeach other via the piezoelectric/electrostrictive body 2 (or 3), and avalue of a ratio of the areas (areas of formed surfaces) in which theelectrodes are disposed is preferably 0.5 to 2, more preferably 0.67 to1.5, and especially preferably 0.83 to 1.2. It is to be noted that inFIGS. 9 to 11, the symbol P denotes a width of a lower electrode, Qdenotes a width of an intermediate electrode, and R denotes a width ofan upper electrode, respectively.

In the piezoelectric/electrostrictive device of the present embodiment,the thickness of the electrode is preferably 15 μm or less, morepreferably 5 μm or less. When the thickness exceeds 15 μm, the electrodefunctions as a relaxing layer, and the flexural displacement issometimes reduced. It is to be noted that the thickness of the electrodemay be 0.05 μm or more from the viewpoint that a substantial function ofthe electrode is exhibited.

Next, there will be described a method of preparing thepiezoelectric/electrostrictive porcelain composition according to thepresent invention. First, a method of preparing apiezoelectric/electrostrictive porcelain composition component containedin the piezoelectric/electrostrictive porcelain composition isdescribed. To prepare the piezoelectric/electrostrictive porcelaincomposition component, first, raw materials such as an oxide of anelement PbO, MgO, Nb₂O₅, TiO₂, ZrO₂, or NiO, and carbonate are weighedso as to obtain a desired composition, and they are mixed by a mixingmethod such as ball milling with some water to obtain a mixed slurry.Subsequently, the resultant slurry can be dried by using a drier or afilter to obtain a mixed raw material. When the resultant mixed rawmaterial is calcined and ground, the piezoelectric/electrostrictiveporcelain composition component (first particles) having desiredparticle diameters can be prepared. It is to be noted that the calciningmay be performed at a temperature of 750 to 1300° C. The grinding may beperformed by a method such as ball milling.

Next, a method of preparing the lead germanate contained in thepiezoelectric/electrostrictive porcelain composition is described. Toprepare the lead germanate, first, raw materials such as PbO and GeO₂are weighed so as to obtain a desired composition, and they are mixed bya mixing method such as ball milling with some water to obtain a mixedslurry. Subsequently, the resultant mixed slurry can be dried by using adrier or the filter to obtain a mixed raw material. After the resultantmixed raw material is calcined at 500 to 900° C., it is ground by amethod such as ball milling. Accordingly, lead germanate (secondparticles) having desired particle diameters can be prepared.

The prepared piezoelectric/electrostrictive porcelain compositioncomponent and lead germanate are weighed, respectively, to obtain adesired ratio, and mixed by a mixing method such as ball milling withsome water to obtain a mixed slurry. The resultant mixed slurry can bedried by using a drier, a filter press or the like to prepare thepiezoelectric/electrostrictive porcelain composition of the presentembodiment. As to the prepared piezoelectric/electrostrictive porcelaincomposition, in a diffraction strength by an X-ray diffraction device, aratio of the strength of the strongest diffraction line of a pyrochlorephase to that of the strongest diffraction line of a perovskite phase ispreferably 5% or less, more preferably 2% or less.

Moreover, an average particle diameter of thepiezoelectric/electrostrictive porcelain composition is preferably 0.07to 1 μm, and more preferably 0.1 to 0.7 μm. It is to be noted that theparticle diameter may be adjusted by thermally treating powder of thepiezoelectric/electrostrictive porcelain composition at 400 to 750° C.In this case, finer particles are integrated with the other particles toconstitute the powder having a uniform grain diameter, and it ispreferably possible to form the piezoelectric/electrostrictive bodyhaving the uniform particle diameter. The piezoelectric/electrostrictiveporcelain composition may be prepared by an alkoxide process, acoprecipitation process or the like.

Next, an embodiment of a first method of manufacturing apiezoelectric/electrostrictive device of the present invention isdescribed. The first method of manufacturing thepiezoelectric/electrostrictive device is a method of manufacturing apiezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body and an electrode electricallyconnected to the piezoelectric/electrostrictive body, comprising thesteps of mixing and sintering first particles containing, as a majorcomponent, a piezoelectric/electrostrictive porcelain compositioncomponent including a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition and NiO or including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, and containing second particles formed of lead germanate tothereby form a piezoelectric/electrostrictive body.

In the first method of manufacturing the piezoelectric/electrostrictivedevice of the present invention, the first particles contain, as themain component, the piezoelectric/electrostrictive porcelain compositioncomponent including NiO or a predetermined ternary solid solution systemcomposition containing an Ni element in a structure thereof. Therefore,it is possible to manufacture the piezoelectric/electrostrictive devicehaving a piezoelectric/electrostrictive body in which a hetero-phase isinhibited from being formed and in which a ratio occupied by theperovskite phase contributing to an electric field induced strain islarge and which has satisfactory piezoelectric/electrostrictivecharacteristics. Since the first particles are mixed with the secondparticles formed of lead germanate, the particles can be sintered at alower temperature. Therefore, it is possible to manufacture thepiezoelectric/electrostrictive device provided with thepiezoelectric/electrostrictive body which is dense and superior incrystallinity without causing a composition deviation or the like.

In the first method of manufacturing the piezoelectric/electrostrictivedevice of the present embodiment, it is preferable to set an averageparticle diameter of the second particles to be smaller than that of thefirst particles. This is because it is possible to manufacture thepiezoelectric/electrostrictive device provided with thepiezoelectric/electrostrictive body in which evenness is not easilygenerated in a distribution of grain boundary phases containing leadgermanate as a major component and which entirely exhibits uniformpiezoelectric/electrostrictive characteristics.

Moreover, from the viewpoint of avoiding deviation in the distributionof the grain boundary phase and which exhibits entirely uniformpiezoelectric/electrostrictive characteristics, the average particlediameter of the second particles is preferably 70% or less, morepreferably 40% or less of that of the first particles.

In the first method of manufacturing the piezoelectric/electrostrictivedevice of the present invention, the first and second particles arepreferably mixed and fired to thereby form thepiezoelectric/electrostrictive body into a film shape and solidly attachthe body onto the substrate made of a ceramic directly or via thefilm-like electrode. In this case, it is possible to manufacture aso-called piezoelectric/electrostrictive film type device in which thepiezoelectric/electrostrictive body and the electrode have film-likeshapes. It is to be noted that details of the method of manufacturing apiezoelectric/electrostrictive film type element will be describedlater.

Next, the second method of manufacturing apiezoelectric/electrostrictive device according to the present inventionis described. The second method of manufacturing thepiezoelectric/electrostrictive device of the present invention is amethod of manufacturing a piezoelectric/electrostrictive device providedwith a piezoelectric/electrostrictive body and an electrode electricallyconnected to the piezoelectric/electrostrictive body, comprising thesteps of mixing first particles containing, as a major component, apiezoelectric/electrostrictive porcelain composition componentcontaining a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solutionsystem composition and NiO, or a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, and second particles formed of lead germanate to obtain amixture, calcining the resultant mixture at 550 to 900° C. to obtain acalcined body, grinding the resultant calcined body to obtain groundparticles, and sintering the resultant ground particles to thereby forma piezoelectric/electrostrictive body.

Here, there will be generally described a method of preparing thepiezoelectric/electrostrictive body having a portion which is notbrought into contact with a grain boundary phase that contains leadgermanate as the main component in an outer edge ofpiezoelectric/electrostrictive porcelain grains in an arbitrary cutsection. To prepare such a piezoelectric/electrostrictive body, first,powder of the piezoelectric/electrostrictive porcelain compositioncomponent obtained by mixing, calcining, and grinding the raw materialsis thermally treated at 1100° C. to 1300° C. Accordingly, grain growthand necking between the particles are caused to obtain a thermallytreated material. Subsequently, this thermally treated material ispounded in a mortar to thereby obtain secondary particles connected toapproximately several primary particles. According to theabove-described method using the secondary particles (powder of thepiezoelectric/electrostrictive porcelain composition component) obtainedin this manner, and powder of lead germanate, it is possible to preparea piezoelectric/electrostrictive body having the portion which is notbrought into contact with the grain boundary phase in the outer edge ofthe piezoelectric/electrostrictive porcelain grain in the arbitrary cutsection.

The powder of the piezoelectric/electrostrictive porcelain compositioncomponent obtained by calcining and grinding still has a lowcrystallinity, and the piezoelectric/electrostrictive characteristics ofthe powder are low. Therefore, in the case where the powder of thepiezoelectric/electrostrictive porcelain composition component isthermally treated at a temperature (e.g., 1100 to 1300° C.) that ishigher than the calcining temperature to enhance the crystallinity, evenwhen the powder is sintered at a low temperature, it is possible toobtain a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having highpiezoelectric/electrostrictive characteristics. It is to be noted thatwhen the thermally treated material is ground too finely, a remainingstress layer is generated on the surfaces of the resultant secondaryparticles by stress during the grinding, and the crystallinity issometimes deteriorated. Therefore, the powder is prevented from beingground excessively, and as a result, a necking portion is preferablyleft. Instead of leaving the necking portion or grinding grain grownprimary particles, a contact area between thepiezoelectric/electrostrictive porcelain particles due to lead germanatemay be reduced, or an amount of lead germanate for use may be reduced toprevent deteriorations of piezoelectric/electrostrictive characteristicsof the resultant piezoelectric/electrostrictive body or device.

In the second method of manufacturing the piezoelectric/electrostrictivedevice of the present invention, the predetermined particles are usedwhich contain, as the main component, the piezoelectric/electrostrictiveporcelain composition component including NiO or a predetermined ternarysolid solution system composition containing an Ni element in astructure thereof. Therefore, it is possible to manufacture apiezoelectric/electrostrictive device having apiezoelectric/electrostrictive body in which a hetero-phase is inhibitedfrom being formed and in which a ratio occupied by the perovskite phasecontributing to an electric field induced distortion is large and whichhas satisfactory piezoelectric/electrostrictive characteristics. In thesecond method of manufacturing the piezoelectric/electrostrictive deviceof the present invention, the ground particles for use are preferablypiezoelectric/electrostrictive composition particles containing thepiezoelectric/electrostrictive porcelain composition component as themain component and 30% or more by mass of coated particles at least apart of whose outer peripheral surface is coated with lead germanate. Byusing piezoelectric/electrostrictive porcelain particles having suchcomposition and structural characteristics, the particles can besintered at a lower temperature. It is possible to manufacture apiezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body which is dense and superior incrystallinity without causing deviation of the composition. It is to benoted that a ratio of the coated particles occupying thepiezoelectric/electrostrictive porcelain composition particles (groundparticles) for use is preferably 50% by mass or more, more preferably70% by mass or more, and especially preferably 100% by mass.

The piezoelectric/electrostrictive porcelain composition particles whosecontent of coated particles is 30% by mass or more can be prepared bygrinding the piezoelectric/electrostrictive body prepared by the methoddescribed above in the method of manufacturing thepiezoelectric/electrostrictive body. When coated particles are used, itis possible to manufacture a piezoelectric/electrostrictive deviceprovided with a piezoelectric/electrostrictive body in which unevennessis not easily generated in the distribution of the grain boundary phasecontaining lead germanate as the main component and which exhibitsentirely uniform piezoelectric/electrostrictive characteristics.

After sintering, polarization treatment is performed using appropriateconditions. In the polarization treatment, heating is preferablyperformed by a known technology. The heating temperature depends on theCurie point of the piezoelectric/electrostrictive porcelain, and ispreferably set at 40 to 200° C.

Moreover, to form the overall shape of thepiezoelectric/electrostrictive body into a sheet shape, after adding aplasticizer, a dispersant, a solvent or the like to thepiezoelectric/electrostrictive porcelain composition, and forming thecomposition into a slurry using a general mixing device such as a ballmill, the slurry can be molded into a sheet shape by use of a generalsheet molding machine such as a doctor blade.

Next, a specific mode of a method of manufacturing apiezoelectric/electrostrictive device (piezoelectric/electrostrictivefilm type device) is described in which thepiezoelectric/electrostrictive body and the electrode have film-likeshapes. First, a layer formed of a piezoelectric/electrostrictiveporcelain composition is formed on a substrate made of a ceramic or theelectrode formed on the surface of the substrate. Examples of a methodof forming the electrode include ion beam, sputtering, vacuumevaporation, PVD, ion plating, CVD, plating, aerosol deposition, screenprinting, spraying, and dipping. Above all, sputtering or screenprinting are preferable with respect to bonding the substrate and thepiezoelectric/electrostrictive body. As to the formed electrode, anappropriate temperature is selected depending on the material or formingmethod of the electrode, and the electrode can be formed integrally withthe substrate and/or the piezoelectric/electrostrictive body by thethermal treatment at about 500 to 1400° C. This thermal treatment may beperformed every time the electrode is formed, but may be performedtogether during the sintering of a layer formed of thepiezoelectric/electrostrictive porcelain composition. However, afterforming the layer formed of the piezoelectric/electrostrictive porcelaincomposition, the thermal treatment is not performed at a temperaturewhich exceeds a sintering temperature of the layer formed of thepiezoelectric/electrostrictive porcelain composition.

Examples of a method of forming the layer formed of thepiezoelectric/electrostrictive porcelain composition on the substrateinclude ion beam, sputtering, vacuum evaporation, PVD, ion plating, CVD,plating, sol-gel, aerosol deposition, screen printing, spraying, anddipping. Above all, screen printing is preferable because it is possibleto easily and continuously form the layer into a high-precision shapeand thickness. It is to be noted that to prepare apiezoelectric/electrostrictive film type device that is provided with aplurality of piezoelectric/electrostrictive bodies and electrodes thatare alternately sandwiched and laminated, the electrode is formed on thelayer formed of the piezoelectric/electrostrictive porcelain compositionformed on the substrate by a method similar to the above-describedmethod. It is to be noted that on this electrode, the layers formed ofthe piezoelectric/electrostrictive porcelain compositions, and theelectrodes are alternately and repeatedly formed until desired multiplelayers are obtained.

Thereafter, a laminate obtained by alternately laminating the layersformed of the piezoelectric/electrostrictive porcelain compositions andthe electrodes on the substrate is integrally sintered. According to thesintering, the film-like piezoelectric/electrostrictive body can besolidly attached onto the substrate directly or via the film-likeelectrode. It is to be noted that the sintering does not necessarilyhave to be integrally performed, and may be successively performed everytime one layer formed of the piezoelectric/electrostrictive porcelaincomposition is formed, but it is preferable to integrally sinter thelaminate including the electrodes from the viewpoint of productionefficiency.

In this case, the sintering temperature is preferably 800 to 1250° C.,more preferably 900 to 1200° C. When the temperature is less than 800°C., the substrate or the electrode is incompletely solidly attached tothe piezoelectric/electrostrictive body, and density of thepiezoelectric/electrostrictive body becomes insufficient in some cases.When the temperature exceeds 1250° C., excessive reactions occur betweenthe piezoelectric/electrostrictive porcelain composition containing thePbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition and NiO or the Pb(Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ternary solid solution system composition and lead germanate, and thepiezoelectric/electrostrictive characteristics of the resultantpiezoelectric/electrostrictive body are sometimes deteriorated. Themaximum temperature holding time during sintering is preferably oneminute or more and ten hours or less, more preferably five minutes andfour hours or less. When the maximum temperature holding time is lessthan one minute, the piezoelectric/electrostrictive body is easilyinsufficiently densified, and desired characteristics cannot be obtainedin some cases. When the maximum temperature holding time exceeds tenhours, a disadvantage sometimes occurs in that thepiezoelectric/electrostrictive characteristics are deteriorated.

Thereafter, a polarization treatment is performed using appropriateconditions. In the polarization treatment, heating is preferablyperformed by a known technology. The heating temperature depends on theCurie point of a piezoelectric/electrostrictive porcelain, and ispreferably set at 40 to 200° C.

EXAMPLES

The present invention will be specifically described hereinafter basedon examples, but the present invention is not limited to these examples.There will be described hereinafter methods of measuring variousphysical values.

Bulk Density: The bulk density was measured with respect to a sinteredbody (piezoelectric/electrostrictive body) by the Archimedes process.

Electric Field Induced Strain: A strain gauge was attached onto anelectrode, and the amount of strain in a direction perpendicular to anelectric field in a case where a voltage of 3 kV/mm was applied wasmeasured as an electric field induced strain (ppm).

d₃₁ Constant: This constant was measured according to Japan ElectronicMaterial Industrial Association standard “Piezoelectric Ceramic VibratorElectric Test Method EMAS-6100”.

Durability: The ratio of the polarization value remaining after the testwith respect to the polarization value before the test was measured asdurability in a case where an electric field of 3 kV/mm was applied to apiezoelectric/electrostrictive body by means of an alternate current 10⁹times.

Flexural Displacement: A voltage was applied between the electrodes of apiezoelectric/electrostrictive film type device so as to obtain anelectric field of 3 kV/mm, and a generated flexural displacement (μm)was measured with a laser displacement measurement unit.

Electric Field Induced Strain Fluctuation: Electric field inducedstrains of 20 samples were measured, and the difference between amaximum value and a minimum value of the measured electric field inducedstrains was obtained as an “electric field induced strain fluctuation.”

Example 1

Raw materials such as an oxide of PbO, MgO, Nb₂O₅, TiO₂, ZrO₂, or NiOwere weighed and mixed so as to obtain a desired composition ratio, anda mixed raw material was prepared. After the mixed raw material wascalcined at 1000° C., the material was ground by a ball mill, and thefirst particles were prepared which contained as a major component apiezoelectric/electrostrictive porcelain composition componentincluding: a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solutionsystem composition having a composition ratio of 20:43:37 (mass ratio);and 0.5% by mass of NiO.

Next, raw materials such as PbO and GeO₂ were weighed and mixed so as toobtain a predetermined composition ratio, and the mixed raw material wasprepared. After calcining this mixed raw material at 600° C., thematerial was ground in a ball mill to prepare the second particlesformed of lead germanate (hereinafter referred to simply as “PGO”) whosecomposition was represented by PbGeO₃. The first and second particleswere weighed and mixed so that the PGO content was 0.5% by mass, and amixed slurry was obtained. The resultant mixed slurry was dried using adrier to obtain a powder of the piezoelectric/electrostrictive porcelaincomposition. The resultant powder of the piezoelectric/electrostrictiveporcelain composition was compressed and molded into a green compacthaving a diameter of 20 mm×thickness of 6 mm under a pressure of 0.5t/cm². The resultant green compact was stored in a magnesia container,and sintered at 1050° C. for three hours to obtain a sintered body(piezoelectric/electrostrictive body). The resultant sintered body wasformed into a size of 12 mm×3 mm×1 mm, opposite surfaces of the bodywere coated with a silver paste to bake, the body was baked to obtain anelectrode, and the electrode was immersed into silicon oil at 70° C.Moreover, a direct-current voltage of 3 kV/mm was applied between theelectrodes for 15 minutes to thereby perform polarization, and thepiezoelectric/electrostrictive device (Example 1) was obtained. Themeasurement results of the physical values of the resultantpiezoelectric/electrostrictive device are shown in Table 1.

Comparative Examples 1 and 2

Piezoelectric/electrostrictive devices (Comparative Examples 1, 2) wereobtained in the same manner as in Example 1 described above except thatthe second particles were not used, and the sintering temperature wasset at a temperature as shown in Table 1. The measurement results of thephysical values of the resultant piezoelectric/electrostrictive devicesare shown in Table 1.

TABLE 1 Composition ratio (mass ratio) of ternary solid NiO PGO Electricsolution system content content Sintering Bulk field induced d₃₁composition ratio PGO ratio temperature density strain constant PMN PZPT (mass %) kind (mass %) (° C.) (g/cm³) (ppm) (×10⁻¹²m/V) Example 1 2043 37 0.5 PbGeO₃ 0.5 1050 7.7 560 −90 Comparative 20 43 37 0.5 None None1050 5.3 Non- Non- Example 1 measurable measurable Comparative 20 43 370.5 None None 1250 7.8 560 −98 Example 2

From the results shown in Table 1, it is apparent that in the case wherethe piezoelectric/electrostrictive porcelain composition containing apredetermined amount of PGO is used, even when the composition issintered at a low temperature of 1050° C., it is possible to manufacturea piezoelectric/electrostrictive device provided with a densepiezoelectric/electrostrictive body having the samepiezoelectric/electrostrictive characteristics as those at a time whenthe composition is sintered at a high temperature of 1250° C. withoutcontaining PGO.

Example 2

Raw materials such as an oxide of an element PbO, MgO, Nb₂O₅, TiO₂,ZrO₂, or NiO were weighed and mixed so as to obtain a predeterminedcomposition ratio. After this mixed raw material was calcined at 1000°C., the material was ground by a ball mill, and first particles wereprepared which contained as a major component apiezoelectric/electrostrictive porcelain composition componentincluding: a Pb(Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition having a composition ratio of 20:43:37 (massratio) and a ratio of Mg and Ni of 87:13 (mass ratio). Apiezoelectric/electrostrictive device (Example 2) was obtained in thesame manner as in Example 1 described above except that the preparedfirst particles of Example 2 were used. The measurement results of thephysical values of the resultant piezoelectric/electrostrictive deviceare shown in Table 2.

Comparative Examples 3 and 4

Piezoelectric/electrostrictive devices (Comparative Examples 3, 4) wereobtained in the same manner as in Example 2 described above except thatsecond particles were not used, and the sintering temperature was set asshown in Table 2. The measurement results of the physical values of theresultant piezoelectric/electrostrictive devices are shown in Table 2.

TABLE 2 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOElectric solution system ratio content Sintering Bulk field induced d₃₁composition (mass PGO ratio temperature density strain constant PMN PZPT ratio) kind (mass %) (° C.) (g/cm³) (ppm) (×10⁻¹²m/V) Example 2 20 4337 87:13 PbGeO₃ 0.5 1050 7.8 830 −163 Comparative 20 43 37 87:13 NoneNone 1050 6.6 340 −105 Example 3 Comparative 20 43 37 87:13 None None1250 7.8 890 −169 Example 4

From the results shown in Table 2, it is apparent that in the case wherethe piezoelectric/electrostrictive porcelain composition containing apredetermined amount of PGO is used, even when the composition issintered at a low temperature of 1050° C., it is possible to manufacturea piezoelectric/electrostrictive device provided with a densepiezoelectric/electrostrictive body having the samepiezoelectric/electrostrictive characteristics as those at a time whenthe composition is sintered at a high temperature of 1250° C. withoutcontaining PGO.

Examples 3 to 6

Piezoelectric/electrostrictive devices (Examples 3 to 6) were obtainedin the same manner as in Example 1 described above except that the Pb inthe piezoelectric/electrostrictive porcelain composition component wasreplaced with a certain kind of replacement element (Sr, Ba, La, or Bi)so as to obtain the replacement ratios shown in Table 3. The measurementresults of the physical values of the resultantpiezoelectric/electrostrictive devices are shown in Table 3.

TABLE 3 Composition ratio (mass ratio) of ternary solid NiO PGO Electricsolution system content content Replacement Bulk field induced d₃₁composition ratio PGO ratio Replacing ratio density strain constant PMNPZ PT (mass %) kind (mass %) element (mol %) (g/cm³) (ppm) (×10⁻¹²m/V)Example 3 20 43 37 0.5 PbGeO₃ 0.5 Sr 5 7.7 540 −105 Example 4 20 43 370.5 PbGeO₃ 0.5 Ba 5 7.7 520 −97 Example 5 20 43 37 0.5 PbGeO₃ 0.5 La 0.57.7 530 −103 Example 6 20 43 37 0.5 PbGeO₃ 0.5 Bi 0.5 7.7 530 −103

From the results shown in Table 3, it is apparent that in the case wherePb is replaced with a predetermined replacement element, it is possibleto manufacture a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having a higher d₃₁ constant.

Examples 7 to 11

Piezoelectric/electrostrictive devices (Examples 7 to 11) were obtainedin the same manner as in Example 2 described above, except that the Tiin the piezoelectric/electrostrictive porcelain composition componentwas replaced with a certain type of replacement element (Nb, Ta, W, orMo) so as to obtain the replacement ratios shown in Table 4. Themeasurement results of the physical values of the resultantpiezoelectric/electrostrictive devices are shown in Table 4.

TABLE 4 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOsolution system ratio content Replacement Bulk composition (mass PGOratio Replacing ratio density Durability PMN PZ PT ratio) kind (mass %)element (mol %) (g/cm³) (%) Example 7 20 43 37 87:13 PbGeO₃ 0.5 None —70 Example 8 20 43 37 87:13 PbGeO₃ 0.5 Nb 5 7.8 85 Example 9 20 43 3787:13 PbGeO₃ 0.5 Ta 5 7.8 80 Example 10 20 43 37 87:13 PbGeO₃ 0.5 W 57.7 77 Example 11 20 43 37 87:13 PbGeO₃ 0.5 Mo 5 7.8 78

From the results shown in Table 4, it is apparent that in the case whereTi is replaced with a predetermined replacing element, it is possible tomanufacture a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having higher durability.

Examples 12 to 14

Piezoelectric/electrostrictive devices (Examples 12 to 14) were obtainedin the same manner as in Example 1 described above, except that thecertain kind of compound (MnO₂, CeO₂, or SiO₂) was included so as toobtain the content ratios shown in Table 5. The measurement results ofthe physical values of the resultant piezoelectric/electrostrictivedevices are shown in Table 5.

TABLE 5 Composition ratio (mass ratio) of ternary solid NiO PGO Electricsolution system content content Content Bulk field induced d₃₁composition ratio PGO ratio Content ratio density strain constant PMN PZPT (mass %) kind (mass %) compound (mass %) (g/cm³) (ppm) (×10⁻¹²m/V)Example 12 20 43 37 0.5 PbGeO₃ 0.5 MnO₂ 0.2 7.7 520 −86 Example 13 20 4337 0.5 PbGeO₃ 0.5 CeO₂ 0.2 7.6 560 −92 Example 14 20 43 37 0.5 PbGeO₃0.5 SiO₂ 0.2 7.5 500 −80

From the results shown in Table 5, it is apparent that in the case wherea predetermined content compound is contained, it is possible tomanufacture a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having higherpiezoelectric/electrostrictive characteristics.

Examples 15 to 17

Piezoelectric/electrostrictive devices (Examples 15 to 17) were obtainedin the same manner as in Example 2 described above, except that acertain content compound (MnO₂, CeO₂, or SiO₂) was included so as toobtain the content ratios shown in Table 6. The measurement results ofthe physical values of the resultant piezoelectric/electrostrictivedevices are shown in Table 6.

TABLE 6 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOElectric solution system ratio content Content Bulk field induced d₃₁composition (mass PGO ratio Content ratio density strain constant PMN PZPT ratio) kind (mass %) compound (mass %) (g/cm³) (ppm) (×10⁻¹²m/V)Example 15 20 43 37 87:13 PbGeO₃ 0.5 MnO₂ 0.2 7.8 760 −152 Example 16 2043 37 87:13 PbGeO₃ 0.5 CeO₂ 0.2 7.6 800 −158 Example 17 20 43 37 87:13PbGeO₃ 0.5 SiO₂ 0.2 7.6 730 −146

From the results shown in Table 6, it is apparent that in the case wherea predetermined content compound is contained, it is possible tomanufacture a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having higherpiezoelectric/electrostrictive characteristics.

Examples 18 to 22, Comparative Example 5

Piezoelectric/electrostrictive devices (Examples 18 to 22, ComparativeExample 5) were obtained in the same manner as in Example 2 describedabove, except that PGO was contained so as to obtain the content ratiosshown in Table 7 (with the proviso that PGO was not contained inComparative Example 5). The measurement results of the physical valuesof the resultant piezoelectric/electrostrictive devices are shown inTable 7.

TABLE 7 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOElectric solution system ratio content Bulk field induced composition(mass PGO ratio density strain PMN PZ PT ratio) kind (mass %) (g/cm³)(ppm) Comparative 20 43 37 87:13 None None 6.6 340 Example 5 Example 1820 43 37 87:13 PbGeO₃ 0.3 7.8 800 Example 19 20 43 37 87:13 PbGeO₃ 1.87.8 720 Example 20 20 43 37 87:13 PbGeO₃ 3 7.8 620 Example 21 20 43 3787:13 PbGeO₃ 4 7.8 540 Example 22 20 43 37 87:13 PbGeO₃ 6 7.8 490

From the results shown in Table 7, it is apparent that in the case wherea PGO content ratio is set within a predetermined range, typically 0.3to 4% by mass, preferably 0.3 to 3% by mass, and more preferably 0.3 to1.8 by mass, it is possible to manufacture apiezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having higherpiezoelectric/electrostrictive characteristics.

Examples 23 to 27

Piezoelectric/electrostrictive devices (Examples 23 to 27) were obtainedin the same manner as in Example 2 described above, except that certainkinds of PGO were contained so as to obtain content ratios shown inTable 8. The measurement results of the physical values of the resultantpiezoelectric/electrostrictive devices are shown in Table 8.

TABLE 8 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOElectric solution system ratio content Bulk field induced d₃₁composition (mass PGO ratio density strain constant PMN PZ PT ratio)kind (mass %) (g/cm³) (ppm) (×10⁻¹²m/V) Example 23 20 43 37 87:13 PbGeO₃0.5 7.8 830 −163 Example 24 20 43 37 87:13 Pb₅Ge₃O₁₁ 0.5 7.9 870 −179Example 25 20 43 37 87:13 Pb₃GeO₅ 0.5 7.8 840 −169 Example 26 20 43 3787:13 Eutectic crystal of 0.5 7.8 820 −160 PbGeO₃ and Pb₅Ge₃O₁₁ Example27 20 43 37 87:13 Eutectic crystal of 0.5 7.9 850 −183 Pb₅Ge₃O₁₁ andPb₃GeO₅

From the results shown in Table 8, it is apparent that in the case whereany of the above-described kinds of PGO is contained, it is possible tomanufacture a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having higherpiezoelectric/electrostrictive characteristics.

Example 28

A lower electrode (dimension: 1.2×0.8 mm, thickness: 3 μm) made of70Ag-30Pd was formed by a screen printing process on a substrate(dimension of thin portion: 1.6×1.1 mm, thickness: 10 μm) made of Y₂O₃stabilized zirconia whose thin portion was flat. The electrode wasthermally treated at 1100° C. for two hours, and formed integrally withthe substrate. Subsequently, a piezoelectric/electrostrictive porcelaincomposition was obtained in the same manner as in Example 2 describedabove, except that the PGO content ratio was set to 1% by mass, andlaminated on the electrode by screen printing to obtain a laminatehaving the dimensions of 1.3×0.9 mm and a thickness of 15 μm. Thislaminate was placed in a container and thermally treated at 1050° C. fortwo hours. Next, after forming an upper electrode (dimension: 1.2×0.8mm, thickness: 0.5 μm) made of Au on an uppermost portion of thelaminate by screen printing, thermal treatment was performed tomanufacture a piezoelectric/electrostrictive device (Example 28). Themeasurement result of the flexural displacement of the manufacturedpiezoelectric/electrostrictive device is shown in Table 9.

Comparative Example 6

A piezoelectric/electrostrictive film type device (Comparative Example6) was obtained in the same manner as in Example 3 described above,except that the piezoelectric/electrostrictive porcelain composition didnot contain PGO. The measurement result of the flexural displacement ofthe manufactured piezoelectric/electrostrictive film type device isshown in Table 9.

TABLE 9 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOsolution system ratio content Flexural composition (mass PGO ratiodisplacement PMN PZ PT ratio) kind (mass %) (μm) Example 28 20 43 3787:13 PbGeO₃ 1 1.3 Comparative 20 43 37 87:13 None None —*¹ Example 6^(*1)not densified, short-circuit defect generated between upper andlower electrodes

From the results shown in Table 9, it is apparent that in the case wherethe piezoelectric/electrostrictive porcelain composition containing apredetermined amount of PGO is used, even when the composition issintered at a low temperature of 1050° C., it is possible to form adenser piezoelectric/electrostrictive body and manufacture apiezoelectric/electrostrictive device capable of obtaining a higherdisplacement.

Examples 29 to 31

There were prepared particles formed of a piezoelectric/electrostrictiveporcelain composition having a value of coating ratio (PGO coatingratio) with PGO on an outer peripheral surface as shown in Table 10 andcontaining as a major component a piezoelectric/electrostrictiveporcelain composition component including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition having an Ni replacement ratio of 13 mol %. These particleswere compressed and molded into a having a diameter of 20 mm×thickness 6mm under a pressure of 0.5 t/cm². The resultant molded green compact wasstored in a magnesia container and sintered at 1050° C. for three hoursto obtain a sintered body (piezoelectric/electrostrictive body. Next,after forming the resultant sintered body into a size of 12 mm×3 mm×1mm, electrodes were formed on opposite surfaces of the body by goldsputtering, and immersed into silicon oil at 70° C. Moreover, adirect-current voltage of 3 kV/mm was applied between the electrodes for15 minutes to perform polarization, and piezoelectric/electrostrictivedevices (Examples 29 to 31) were obtained. The measurement results ofthe electric field induced strain fluctuations of the resultantpiezoelectric/electrostrictive devices are shown in Table 10.

TABLE 10 Composition ratio (mass ratio) of ternary solid Mg:Ni PGO PGOElectric field solution system ratio content coating induced straincomposition (mass PGO ratio ratio fluctuation PMN PZ PT ratio) kind(mass %) (%) (ppm) Example 29 20 43 37 87:13 PbGeO₃ 1 0 50 Example 30 2043 37 87:13 PbGeO₃ 1 40 50 Example 31 20 43 37 87:13 PbGeO₃ 1 80 30

From the results shown in Table 10, it is apparent that in the casewhere the particles having a large PGO coating ratio and formed of thepiezoelectric/electrostrictive porcelain composition are used, it ispossible to manufacture a piezoelectric/electrostrictive device providedwith the piezoelectric/electrostrictive body having small electric fieldinduced strain fluctuations.

Examples 32 to 35

There were prepared first particles in the same manner as in Example 2described above, which contained as a major component apiezoelectric/electrostrictive porcelain composition component includinga Pb (Mg, Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solutionsystem composition having an Ni replacement ratio of 13 mol %.Piezoelectric/electrostrictive devices (Examples 32 to 35) were obtainedin the same manner as in Example 1 described above, except that theabove particles were used, second particles prepared in the same manneras in Example 1 and formed of PGO having certain particle diameters werealso used, and the particles were weighed and mixed so as to obtain aratio (second/first(%)) of particle diameters of the second particleswith respect to those of the first particles as shown in Table 11. Themeasurement results of the electric field induced strain fluctuations ofthe resultant piezoelectric/electrostrictive devices are shown in Table11.

TABLE 11 Composition ratio (mass ratio) of ternary solid Mg:Ni PGOParticle Electric field solution system ratio content diameter ratioinduced strain composition (mass PGO ratio (first/second) fluctuationPMN PZ PT ratio) kind (mass %) (%) (ppm) Example 32 20 43 37 87:13PbGeO₃ 1 110 110 Example 33 20 43 37 87:13 PbGeO₃ 1 80 80 Example 34 2043 37 87:13 PbGeO₃ 1 50 50 Example 35 20 43 37 87:13 PbGeO₃ 1 30 20

From the results shown in Table 11, it is apparent that it is possibleto manufacture a piezoelectric/electrostrictive device provided with apiezoelectric/electrostrictive body having a smaller electric fieldinduced strain fluctuation in a case where the ratio (first/second (%))of the particle diameters of the first particles with respect to thoseof the second particles is smaller.

According to the present invention, a piezoelectric/electrostrictivedevice is provided which has superior piezoelectric/electrostrictivecharacteristics, and which is suitable for an actuator, a sensor or thelike.

1. A method of manufacturing a piezoelectric/electrostrictive devicehaving a piezoelectric/electrostrictive body and an electrodeelectrically connected to the piezoelectric/electrostrictive body, themethod comprising the steps of: mixing and sintering first particlescontaining, as a major component, a piezoelectric/electrostrictiveporcelain composition component including aPbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition and NiO or including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, with lead germanate particles, to thereby form thepiezoelectric/electrostrictive body.
 2. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 1, wherein anaverage particle diameter of the lead germanate particles is smallerthan that of the first particles.
 3. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 1, wherein thefirst particles and the lead germanate particles are mixed and sinteredto thereby form the piezoelectric/electrostrictive body having a filmshape, and to attach the piezoelectric/electrostrictive body onto aceramic substrate directly or via the electrode.
 4. A method ofmanufacturing a piezoelectric/electrostrictive device having apiezoelectric/electrostrictive body and an electrode electricallyconnected to the piezoelectric/electrostrictive body, the methodcomprising the steps of: mixing first particles containing, as a majorcomponent, a piezoelectric/electrostrictive porcelain compositioncomponent including a PbMg_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solidsolution system composition and NiO or including a Pb(Mg,Ni)_(1/3)Nb_(2/3)O₃—PbZrO₃—PbTiO₃ ternary solid solution systemcomposition, with lead germanate particles to obtain a mixture;calcining the mixture at a temperature in a range of 550° C. to 900° C.to obtain a calcined body; grinding the calcined body to obtain groundparticles; and sintering a shaped body of ground particles to form thepiezoelectric/electrostrictive body.
 5. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 4, wherein theground particles are piezoelectric/electrostrictive porcelain particlescontaining the piezoelectric/electrostrictive porcelain compositioncomponent as a major component, and wherein 30 mass % or more of coatedparticles, at least a part of which are located on an outer peripheralsurface of the piezoelectric/electrostrictive body, are coated with leadgermanate.
 6. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 4, wherein theground particles are sintered to form the piezoelectric/electrostrictivebody having a film shape and to attach thepiezoelectric/electrostrictive body onto a substrate made of a ceramic,either directly or via the electrode.
 7. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 1, wherein thelead germanate particles are at least one kind of lead germanateparticles selected from the group consisting of PbGeO₃, Pb₅Ge₃O₁₁,Pb₃GeO₅, an eutectic of PbGeO₃ and Pb₅Ge₃O₁₁, and an eutectic ofPb₅Ge₃O₁₁ and Pb₃GeO₅.
 8. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 4, wherein thelead germanate particles are at least one kind of lead germanateparticles selected from the group consisting of PbGeO₃, Pb₅Ge₃O₁₁,Pb₃GeO₅, an eutectic of PbGeO₃ and Pb₅Ge₃O₁₁, and an eutectic ofPb₅Ge₃O₁₁ and Pb₃GeO₅.
 9. The method of manufacturing thepiezoelectric/electrostrictive device according to claim 1, wherein thefirst particles are thermally treated at a temperature in a range of1100° C. to 1300° C. before the first and second particles are mixed.10. The method of manufacturing the piezoelectric/electrostrictivedevice according to claim 4, wherein the first particles are thermallytreated at a temperature in a range of 1100° C. to 1300° C. before thefirst and second particles are mixed.